(1) Field of the Invention
The invention is directed to a hydraulically set packer mechanism having particular application for use in horizontal sections of deviated subterranean wells, the packer mechanism including an emergency disconnect at the top of the apparatus and a releasing mechanism at the bottom.
(2) Brief Description of the Prior Art
Subsequent to the drilling of a subterranean oil or gas well, a string of tubular conduit commonly referred to as "casing" is run into the well. Thereafter, the casing is cemented into place. After the cementing operation, it is necessary to perforate the well so that production fluids within the production zone may flow from the production zone, through holes perforated through the cement behind the casing, into holes in the casing, and through the well bore to the top of the well.
For many years the desirability of utilizing a subterranean wellbore having a non-vertical or horizontal portion traversing a production formation has been known and appreciated in the prior art. Laterally directed bores are drilled radially, usually horizontally from the primary vertical wellbore, in order to increase contact with the production formation.
Most production formations have a substantial horizontal portion and, when conventional vertical wellbores are employed to tap such production formations, a large number of vertical bores must be employed. With the drilling of a wellbore having a non-vertical or horizontal portion traversing the production formation, a much greater area of the production formation may be traversed by the wellbore and the total drilling costs in the field may be substantially decreased. Additionally, after a particular horizontal wellbore has produced all of the economically available hydrocarbons, the same vertical wellbore may be re-drilled to establish another horizontal portion extending in another direction and thus prolong the utility of the vertical portion of the well and increase the productivity of the well to include the total production formation.
By use of and reference to the phrase "wellbore" herein, it is intended to include both cased and uncased wells. When uncased wells are completed, the bore hole wall defines the maximum hole diameter at a given location. When cased wells are completed, the "wall" of the well will be the internal diameter of the casing conduit.
By use of the phrase "deviated well" and "deviated wellbore", it is meant to refer to wells and wellbores which comprise a vertical entry section communicating through a relatively short radius curvature portion with a non-vertical or horizontal portion communicating with the production formation. In most instances, the production formation extends for a substantial horizontal extent and the generally linear wellbore portion traverses a substantial horizontal extent of the production formation, at least up to a distance of 1000 to 2000 feet, or more. The radius portion of the wellbore has a curvature of at least 10.degree. per 100 feet of length, and preferably a curvature lying in the range of 10.degree. to 30.degree. per 100 feet of length.
In some aspects, the present invention is not limited to use in horizontal completions of deviated wells and can be used in conventional or straight hole subterranean wells.
In co-pending application Ser. No. 345,107, filed on the same date as the present application, entitled "Method and Apparatus for Selective Retraction of a Tubing Carried Perforating Gun", there is disclosed an apparatus having particular utility for use in horizontal completions of subterranean wells for retracting tubing carried perforating guns. That apparatus is intended to be utilized with a completion packer mechanism which is carried into the well on a tubular workstring, the workstring having positioned thereabove a service retrievable packer. Because of the deviation of such horizontal wells, it is quite desirable that the setting mechanism for any permanent packer be hydraulically actuated, thus eliminating the reliance on tubular manipulation during the setting procedure.
The present invention provides a particularly unique packer assembly having particular utility for use in such completion operations and having a tandem piston arrangement operating in concert with companion cylinders for actuating the seal assembly and the anchoring means, or, preferably, slip assembly. The present invention also provides an emergency disconnect provided at the top of the apparatus for disconnecting the apparatus in the event that it becomes stuck in the well, or it is otherwise essential to quickly withdraw the tubular work or other string from the well, leaving the packer either in secured position in the well, or dropped to the bottom thereof if it is unsecured at the time of the emergency disconnect procedure. The invention also contemplates a mechanical release mechanism for actuation in the event that it is desired to release the packer subsequent to acidizing or otherwise remedially treating the formation which has been subsequently perforated.